Releasable screen tensioning and connecting means



ci.. 22, i968 A. M. GRAIN 3,406,823

RELEASABLE SCREEN TENSIONING AND CONNECTING MEANS Filed March 25, 1966 2 Sheets-Sheet 1 INVE NTOR AT TO RN ENS.

Oct. 22, 968

Filed March 25, 1966 A. M. CRAIN RELEASABLE SCREEN TENSIONING AND CONNECTING MEANS 2 Sheets-Sheet 2 .tum/Extra@ /Lduu ATTORM E75,

United States Patent() ABSTRACTV OF THE DSCLGSUR `A'spring for tensioning the screen on a screeningy machine. The spring generally comprises -a U-shaped` portion and a frame engaging portion connected thereto The U- shaped portion comprises two legs joined at their lower ends by a bend, one of the legs at its upper end joining the top of the frame engaging portion, the other of the legs of the U-shaped portion having at its yupper end a screen engagingitip and being yieldable as a spring toward the frame engaging portion. The latter' portion comprises rounded upper and lower lobes connected byl a `flexing section between them which permits the lobes to move relatively towardi one another lto be received in co pression in a channel of the screen frame.

This invention relates to improved means `for resiliently and releasably mounting screens of the type employed in power driven sifting and screening machines.

It is conventional to mount sifting 'screens releasably to their frames, to facilitate cleaning and replacement as necessary, and so that screens of different mesh sizes can be used on the same screen frames. However, prior releasable screen attaching means having been relatively cumbersome to use, or have not in use aiorded altogether complete security against accidental disengagement from the screen or the frame.

Many previous screen tensioning devices have been particularly deficient for use in the food processing industry, where sanitary code regulations may'require the entire product zone of the screening machine to be completely disassembled and cleaned every twenty-four hours or even more frequently. This has presented a need for A screen attaching means which' will permit very simpleand quickvscreen removal and replacement, and which ca n themselves be completely removed from the screen frame to permit thorough cleaning both ofthe tensioning means andV of the frame. Y

In Patent No. 3,081,874, of which the present applicant is one of the joint patentees, there is disclosed screening tensioning means which includes a detent clip-on arrangement for releasablyengaging a screen frame, together with a spring nger for releasably engaging the screen. The present invention is directed'to a tensioner spring which has been found to display further improvements over the device disclosed in said patent, in terms of resistance to fatigue `in use,- security of connection to the screen frame, ease of positioning along the frame, and fabricability in stainless steel. j

It ha's been an important objective of this invention to provide improved screen tensioning apparatus by ,means of which the tensioning spring may be easily removed from a screen frame when desired, but such that if stress present on `'the spring due to the tautness of the screen is suddenly released,the spring will not become disengaged from or ily off of the thescreen frame, thereby preventing possible injury to operatingy personnel and enhancing the vsafety of the apparatus.

It has been a further objective of this invention to provide an improved screen tensioner and a cooperating frame such that both are suitable for manufacture in stainless steel and may 'be easily, thoroughly and quickly cleaned with virtually no chance for particulate material to adhere thereto in cracks or crevices.

It has been a further objective of this invention to provide an improved screen tensioning apparatus wherein the screen tensioners may be attached to the frame at any point therealong and be easily and quickly shifted from one position to another along the screen frame without disengagement therefrom.

In this invention, I have provided a new tensioner spring and a new cooperating frame member. The frame presents an outwardly opening longitudinal channel into which the spring can readily be snapped in place, and from which the spring can easily be removed when desired. However, when the spring engages the screen it is urged into very secure engagement With the frame,V so that there is virtually no tendency for accidental disengagement to occur.

Broadly expressed, the tensioner spring of the invention comprises an integral spring including a frame-engaging portion having rounded upper and lower lobes which face each other and are connected at one side only by a yieldable joining section which can bend to permit the lobes to be brought closer together. The tensioner also includes a portion having two spaced legs joined at the bottom by an arcuate Isection, one leg at its upper end being joined to the upper lobe of the frame-engaging portion opposite the yieldable joining section, the other leg having a screen-engaging portion adjacent its upper end and projecting away from the lobes.

The frame member adapted to mount the spring presents a channel defined by a black wall, spaced upper and lower flanges extending from the back wall, a lip depending from the top flange and a web extending upwardly from the bottom ilange, whereby the spring lobes can be engaged within the frame channel, with the screen-engaging portion of the spring extending beyond the opening between the lip and web of the frame member.

I have also invented an improved sealing means for use with a screen frame which is very rapidly demountable from the frame for cleaning. This strip is joined to a screen frame along an underneath surface thereof, and is generally in the lform of a tube presenting an upwardly opening channel thereinto, and having a relatively narrow neck and an ovaloid internal enlargement for mounting T-shaped mounting studs presented by the frame. The internal cavity of the sealing strip is configured to minimize direct compressional contact between the head of the mounting studs and the'bottom of the cavity.

The invention is further described With reference to the accompanying drawings, in whi-ch:

FIGURE lis a perspective view showing a rectangular wire screen mounted to a screen frame by a plurality of screen tensioners which may be formed in accordance with the invention.

FIGURE 2 is an enlarged cross section taken along line 2-*2 of FIGURE l, and shows la frame member and tensioner spring formed in accordance with a preferred embodiment of the invention.

FIGURE 3 is a side elevation of a tensioner spring of the type shown in FIGURE 2, the spring being in unstressed condition.

lFIGURE 4 is a fragmentary front elevation of the tensioner of FIGURE 3, showing the finger tip which is adapted to engage openings provided in the screen.

FIGURE 5 is a vvertical section of a resilient sealing strip for mounting to a screen frame of the type shown in FIGURE 2.

FIGURE 6 is a vertical section of two screen and frame assemblies with a spacer therebetween, as mounted within a screen box of a typical screening machine.

The screen frame is designated generally at in the drawings, and for purposes of illustration is shown as comprised of four frame members 11, 12, 13 and 14. A screen 15, which may be conventional, is held tautly over the top surface 16 of the frame 10 by a plurality of screen tensioners which are designated generally by 17. It will be noted that the frame may be of any desired overall peripheral configuration, and that a curved or polygonal frame may be used.

Frame members 11-14 may be of similar cross-sectional shape, and each 'preferably has the configuration illustrated in FIGURE 2. By way of example, the frame members may be formed in stainless steel by rolling or on a press brake, or may be extruded in aluminum.

Each frame member has a vertical or back wall portion 18, which at its upper edge adjoins a top flange 19. The upper surface 16 of the top ange 19 defines the surface across which the screen is stretched. At the side of top flange 19 which is opposite to wall 18, a downwardly angulated lip 20 is formed.

Along its lower edge the back wall 18 joins a horizontal bottom flange 21. On the side thereof opposite wall 20, bottom flange 21 joins an upwardly angulated spring retaining web 22 which is spaced from the wall 18 by approximately the same distance as lip 20. Web 22 along its upper edge joins a horizontal shoulder portion 23 which assists in engaging the spring in the channel and which has a downwardly turned outer flange 24. It will be seen that the bottom 21 and the shoulder 23 are parallel but that shoulder 23 is spaced somewhat above the bottom 21, and that the lip 20, top 19, back 18, ybottom 21, and web 22 together define a generally C-shaped channel extending along the outside length of the frame member.

At suitable intervals, e.g. 1-8", mounting studs 26 are secured along the underside of the frame bottom 21. These studs 26 may comprise flat head stainless rivets, and each has a neck portion 27, the upper end 28 of which is suitably secured to the frame member as by a weld or threads. Below the neck portion 27 is an enlarged flat head 29, which may be circular in outline. These studs 26 `position and mount a longitudinal resilient sealing member 35, which will be described in detail hereinafter.

The frame members are secured to one another at their ends 37, for example by welding. When the frame is so assembled, the surfaces of the several top anges 19 should lie in the same plane 16. The frame may include conventional bracing, ball cleaner retainers, etc., not shown.

In use, each tensioner spring 17 is tted into the generally C-shaped compartment dened along the outside of frame members, as seen in FIGURE 2. Each spring 17 may be considered as comprising two integrally connected portions, a mounting or frame engaging portion 39, which in use is received and retained within the C- shaped frame channel, and a screen hook or tensioning portion 40 which includes a tip 41 for engaging the screen. v

As best can be seen in FIGURE 3, in elevation the mounting portion 39 of the spring may be roughly likened to the numeral 3, while the screen tensioning hook 40 may be likened to a letter U, connected at the top of one leg to the top of the mounting portion.

Spring 17 is formed `from a flat strip of suitable spring material; the configuration is such that stainless steel can be used, and in fact stainless is preferable for use in installations subject to severe sanitary limitations. As seen in the front elevation of FIGURE 4, the spring is generally rectangular in outline, with the exception that the tip 41 at the outer or free end of finger 40 is of reduced width to permit easier engagement with cooperating mounting apertures or grommets in screen 15. The spring can be formed by conventional spring making methods, and preferably is formed of a strip having a width which is about 10-12 times its thickness, which relation I have found to be especially effective.

As viewed in side elevation, the spring 17 includes generally semi-circular upper and lower lobes 44 and 45 respectively, joined by a flexible, preferably inwardly bent knee 46, the sides of which form an obtuse angle with one another. At its upper end, one leg 47 of the U-shaped tensioning portion 40 joins upper lobe 44, and at its lower portion leg 47 leads to a semi-circular -bend or arc 48. The bend 48 joins the opposite leg -49 of'the tensioning or U-portion 40. At the upper end of leg 49, the tip 41 is bent angularly outwardly.

The spring height, as measured between lobes 44 and 45, should preferably be just slightly less than the dimension between frame surfaces 19 and 21, so thatthe spring can freely be slid longitudinally along the channel but will be prevented by its own Width from twisting about a horizontal axis. The bottom of the U-bend 48 should in use preferably reside just slightly above frame shoulder surface 23, in order to get the maximum effective spring length in tensioning portion 40. Tip 41 is bent from leg 49 in a position somewhat below'the top surface 16 of the frame, thereby to tension thev spring outwardly and to hold it down on surface 16. In FIGURE 2 the position of spring tensioning portion 40 when not engaged with screen 15 is shown by the dotted lines, its position when engaged with the screen being indicated by the solid lines. The angle through which tensioner portion 40 moves between the stress and unstressed conditions will control the tension exerted on the spring.

Screen 15 is sized to provide an edge portion 52 which projects beyond frame lip 20 to be engaged by spring finger tip 41, in the position indicated by the solid outline in FIGURE 2. In the screen peripheral edge portion 52 a series of openings 53, suitably provided by metalized or rubberized grommets 54, are provided at spaced intervals depending on the size of the screen, its loading, and other operating details. The relation of the sizes of spring tip 41 and the opening 53 in grommets 54 is such that tip 41 is readily engaged within the opening. It is convenient, although not necessary, that tip 41 be bent or bowed slightly in the transverse direction so that it conforms to the curvature of opening 53.

Spring 17 is attrached to the frame by first seating upper lobe 44 in the angle between frame surfaces 18 and 19, with lobe 45 resting on shoulder 23. Lobe 45 is then pushed inwardly over the edge of web 22, which compresses the spring by bending knee 46 to permit lobe 45 to clear the web. When seated, the spring can be slid along the frame to align with a screen opening. Leg 49 is pushed inwardly, bending arc 48, to engage the screen opening 53. Such engagement tends to urge lobe 45 forwardly into secure seating relation against web 22.

I have found in actual tests that, should tip 41 become disengaged from the screen for any reason (e.g. grommet failure) during operation, the spring will nonetheless not accidentally be dislodged from the frame channel, which is a significant safety factor. Removal when desired is effected by prying lower lobe 45 over the upper end of web 22.

The arrows in FIGURE 2 illustrate the general direction of the forces exerted by the spring on the frame when the spring engages the screen, which forces prevent the spring from becoming disengaged from the frame in operation.

It is frequently desirable to stack a plurality of screen frames, one on top of another, in order to classify the particulate material being screened into two or more size ranges. For such use, as well as for another purposes, seals are ordinarily provided between the stacked screen frames in order to prevent material loss over the edge of one screen onto the screen below, and'to preventexternal contamination of the screened products. Hence it has been conventional to permanently attach a sealing strip around the bottom of each screen frame. However,

in modern commercial practice, where very frequent disassembly and cleaning are often mandatory, such sealing strips are unacceptable for the reason that they cannot be removed. v

As shown in FIGURE 2, I have also provided a co'mpletely removable and cleanable sealing means for use with the screen frame. The mounting studs 2-6 engage a resilient cushioning member 35 which is in the form of an upwardly opening block C, which, viewed in section in unstressed condition (FIGURE 5) has a convex lower surface 57, angulated side walls 5,8, 59, and an upwardly openinginternal cavity 60 of generally T-shaped section. In unstressed condition the width of neck 61 between limbs 62 and 63 is somewhat less than the diameter of the neck 27 of mounting stud 26, while internal cavity 60 accommodates the head 29 of lstud 26 so that the upper faces of limbs 62 and 63 engage .the bottom flange 21 of the frame. By reason of the relatively narrow width of gap 61, the limbs 62 and -63 are stressed when the strip 35 is seated on the studs 26.

The resilient member 35 is preferably made of an elastic material `such as neoprene rubber which can withstand steam cleaning. The strip is attached Ato the frame by opening the channel 61 between the left and right limbs 62 and 63 and snapping it over the mounting studs, and can be removed simply by pulling it prependicularly away from the bottom flange 21 of the frame.

It will be noted that the main portion of cavity 60 is ovaloid, having rounded lower surface 64 (see FIG- URE 5) which has a clearance below stud head 29 so that when the strip is compressed the head will not press directly against surface 64 to cause hard spots in the seal.

FIGURE 6 illustrates .the use of screen attaching and sealing means in accordance with this invention in a multiple screen box. In this illustrative embodiment of a typical screen installation, a pair of screens `65 and 66 are secured respectively onto screen frames 67 and 68. Below its lower flange, frame 67 has a downwardly extending spacer `69 leading to a second or `duplicate lower flange porti-on 70 onto which the cushioning member 71 is secured. The cushioning member 72 of the lower screen frame 68 rests on a sanitary liner 73 within a screen box designated generally by 74. The machine also includes a hood or cover 75 having a cushioning member 76 secured to a horizontal flange portion 77 thereof. It will be seen that the cushioning member 76 of the hood 75 rests upon the top screen y6'5 above the top flange 19 of the upper frame 67, thereby providing a sealed` closure.

Having described my invention, I claim: 1. A screen tensioning spring formed of strip spring material,

said spring including a portion for engaging a screen frame and a U-shaped portion connected thereto,

said frame engaging portion comprising two opposed, rounded upper and lower lobes connected at one side only by a. flexing section therebetween permitting said lobes to be moved relatively toward one another to be received by a screen frame, said U-shaped portion comprising two legs joined at their lower ends by a bend, one of said legs at its upper end joining an outer end of said upper lobe,

said bend and the other of said legs projecting away from said lobes,

said other of said legs having at its upper end a screen engaging portion projecting upwardly and away from said upper lobe, said spring engaging portion being yieldable as a spring toward said upper lobe.

2. The spring of claim 1 wherein said flexing section between said lobes is an inwardly bent knee the sides of which form an angle with one another.

3. The spring of claim 1 wherein said lower lobe extends forwardly below said one leg and said bend resides closely above the outer end of said lower lobe when said spring is not stressed.

4. The spring of claim 1 wherein said lobes are semicircular. l

5. The spring of claim 1 wherein said Ascreen engaging portion is bent at an angle to ysaid upper leg.

6. An integral, screen tensioning spring comprising a generally U-shaped portion and a numeral 3-shaped portion,

said U-shaped portion being connected at the top of one leg thereof to the upper end of the numeral 3- shaped portion,

the length of the leg of said U-shaped portion connected to said 3-shaped portion being less than the distance between the upper and lower ends of said 3-shaped portion, the lower end of said 3-shaped portion extending outwardly below said leg,

and means adjacent the top of the other leg of said U-shaped portion for engaging a screen. j

7. A screen frame member and a screen tensioning spring connected therewith,

said frame member presenting a generally C-shaped channel in which said spring is engaged,

said channel being defined by a back wall, top and bottom flanges extending from said back wall, a lip depending from said top flange and a web spaced from said back wall and extending upwardly from said bottom llange,

said spring including a portion engaged in said channel and a U-shaped portion projecting outwardly therefrom,

said channel engaging portion comprising two opposed,

rounded upper and lower lobes connected at one side only by a flexing section therebetween permitting said lobes to be moved relatively toward one an other, said upper and lower lobes being received in said channel between said top and bottom llanges respectively and retained therein by said lip and web respectively,

said U-shaped portion comprising two legs joined at their lower ends by an arc, one of said legs at its upper end joining said upper lobe,

said arc and the other of said legs projecting away from said lobes,

said other of said legs having at its upper end a screen engaging portion, said screen engaging portion being yieldable as a spring toward said upper lobe. 8. The structure of claim 7 wherein said flexing section between said lobes is a knee bending between said lobes and having sides which form an angle with one another.

9. The structure of claim 7 wherein said lower lobe extends below said one leg, and said arc is adjacent the outer end of said lower lobe.

10. The structure of claim 7 which also includes a sealing strip detachably secured to said frame member along the underneath surface of the bottom ilange thereof,

said sealing strip comprising, a flexible member having an internal chamber extending longitudinally therein and a throat having a width smaller than said charnber between said chamber and the top surface of said strip,

said bottom flange having means mounting said sealing strip which pass through said throat and are seated in said cavity.

11. The structure of claim 10 wherein said chamber is ovaloid in section.

12. The structure of claim 11 wherein said mounting means comprise a plurality of rivets secured along said bottom flange,

each said rivet having an enlarged head engaged within said chamber but not engaging the bottom of said chamber.

13. The structure of claim 12 wherein said throat grips said rivets passing therethrough.

14. In a power driven screening machine,

a screen, a screen frame, and a plurality of screen tensioning springs holding said screen in tension onto said frame,

said frame member having a` generally C-shaped channel in which said springs are engaged,

said channel being defined by a back wall, top and botton anges extending from said back wall, a lip depending from said top flange and a web extending upwardly from said bottom ange toward said lip,

each said spring including a portion engaged in said screen frame and a U-shaped portion connected thereto engaging said screen,

fsaid frame-engaging portion comprising two opposed,

` rounded upper and lower lobes connected at one side only by a exing section therebetween permitting said lobes to be compressed toward one another, said lobes being received and retained within said channel,

said U-shaped portion comprising two legs joined'` at ltheir lower ends by a bend, one of said legs at its upper end joining an outer end of said upper lobe,

8 said bend and the other of said legs projecting away from said lobes and channel, said other of said legs at its upper end engaging said spring.

References Cited "UNITED STATES PATENTS 928,006 7/1909 Thomas 24-#73 v1,620,372 3/1927 Mander f 24-73 1,739,057 12p/1929 Bock '.l.' 24-73 Y 2,114,406 4/1938 simpson 209-408 X 2,130,017 9/1938 Lewis 49-494 2,596,780 5/1952 Meyers 1;.- 49-492 X 2,720,014 l 10/1955 ca1dwe11- 24-73 FOREIGN PATENTS 790,960 2/1958 Great'Britain.

HRRY B. THORNTON, Primary Examiner.

20 ROBERT HALPER, Assistant Examihe'r. 

